Health Encyclopedia

Home | List of Topics | General Medical Information | Tests

Sweat electrolytes test

Definition

Sweat electrolytes is a test that measures the level of chloride in sweat.

Alternative Names

Sweat test; Sweat chloride; Iontophoretic sweat test

How the test is performed

In the first part of the test, a colorless, odorless chemical that causes sweating is applied to a small area on an arm or leg. An electrode is then attached to the arm or leg, which allows the technician to apply a weak electrical current to the area to stimulate sweating.

People may feel a tingling sensation in the area, or a feeling of warmth. This part of the procedure lasts approximately 5 minutes.

The next part of the test involves cleaning the stimulated area and collecting the sweat on a piece of filter paper or gauze, or in a plastic coil. After 30 minutes, the collected sweat is sent to a hospital laboratory for analysis. The entire collection procedure takes about 1 hour.

How to prepare for the test

No special preparation is necessary. Make sure the center where the test is being performed is a cystic fibrosis testing center.

How the test will feel

Though the test is not painful, some people describe a tingling sensation at the site of the electrode. In smaller children or infants, the sensation can cause irritability or discomfort.

Why the test is performed

Sweat testing is the standard method for diagnosing cystic fibrosis. People with cystic fibrosis have higher amounts of sodium and chloride in their sweat, which the test can detect.

Some people are referred for testing because of symptoms such as poor growth, many respiratory infections, or foul-smelling stools. In some states, newborn screening programs test for cystic fibrosis, and the sweat test is used to confirm these results.

Normal Values

Normal values are as follows:

• Sodium:
  • Normal: less than 60 mEq/L
  • Abnormal: greater than 90 mEq/L
  • Equivocal: 60 - 90 mEq/L
• Chloride:
  • Normal: less than 40 mEq/L
  • Abnormal: greater than 60 mEq/L
  • Equivocal: 40 - 60 mEq/L

Note: mEq/L = milliequivalent per liter

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What abnormal results mean

An abnormal test may indicate the presence of cystic fibrosis.

References

Behrman RE. Nelson Textbook of Pediatrics. 17th ed. Philadelphia, Pa: WB Saunders; 2004.

LeGrys VA. Diagnostic sweat testing: the Cystic Fibrosis Foundation guidelines. J Pediatr. Jul 2007; 151(1): 85-9.

Review Date:11/12/2007
Reviewed By:Rachel A. Lewis, M.D., F.A.A.P., Columbia University Pediatric Faculty Practice, New York, NY. Review provided by VeriMed Healthcare Network.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is the first of its kind, requiring compliance with 53 standards of quality and accountability, verified by independent audit. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial process. A.D.A.M. is also a founding member of Hi-Ethics (www.hiethics.com) and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).

The Agency for Health Care Administration (Agency) and this website do not claim the information on, or referred to by, this site is error free. This site may include links to websites of other government agencies or private groups. Our Agency and this website do not control such sites and are not responsible for their content. Reference to or links to any other group, product, service, or information does not mean our Agency or this website approves of that group, product, service, or information.

Additionally, while health information provided through this website may be a valuable resource for the public, it is not designed to offer medical advice. Talk with your doctor about medical care questions you may have.